Electron discharge device and associated circuits



May 16, 195o A. v. HAEFF 2,507,972

ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUITS May 16, 195o A. V. HAEFF ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUITS Original Filed July 25, 1942 'o' Sheets-Sheet 2 /MME ml I 1N VENToR. wdw Jing# www@ May 16, 195o A. v. HAEFF 2,507,972

ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUITS Original. Filed July 25, 1942 3 Sheets-Sheet 5 Mum/fag? Patented May 16, 1950 UNITED STATESPATENT OFFICE ELECTRON DISCHARGE DEVICE AND ASSOCIATED CIRCUITS Andrew V. Haef, Washington, D. C., assignor to Radio Corporation oi America, a corporation of Delaware 4 claims. (c1. 315-439) My invention relates to electron discharge devices and associated circuits particularly suitable for ultra high frequencies as high power output tubes which are useful as ampliers or oscilrlators.

This application is a division of my copending application, Serial No. 452,302, iiled July 25, 1942, now Patent 2,400,753, and assigned to the same assignee as the present application.

In electron' discharge devices intended for high power output and particularly for use at ultra high frequencies, close spacing of the electrodes y and high operating voltages are requisites. Optimum operating conditions for maximum output require a maximum instant grid voltage and a minimum instant plate voltage when the peak plate current flows. However, for the usual electron discharge device undesired grid emission due toelectron bombardment from the cathode and heating of the grid by radiated heat from the electron collecting surface of the anode or collector may result. Grid and plate circuit loading, burning out of the grid and increased heating at the anode, which represents wasted energy and hence a lowering of the efficiency of the electron discharge device, may occur under these conditions.

In the case of oscillators either self-biasing resistors may be used or fixed bias may be used to obtain the proper biasing voltage on the grid. Where a self-biasing resistor is used between grid and cathode, when the grid is positive, electrons strike the grid and cause secondary emission, which results in current flowing in the grid circuit. This results in a higher positive bias being placed on the grid, thus further increasing the positive grid potential and the velocity of the electrons bombarding the grid. This building up of the positive bias on the grid may cause the grid to burn out.

In the case of a xed bias, While the bias itself does not increase, nevertheless when the grid is at positive peak and the plate voltage is at a minimum positive voltage, electrons striking the grid cause it to heat up, thus causing emission from the grid. Electrons emitted from This grid` emission current, of course, also loads down the plate circuit, another undesirable factor.

In order to minimize grid emission, lower peak grid voltages are required, which as pointed out. above means higher plate voltages with lower plate efficiency. It is desirable to have the electrons collected by the plate at a low velocity and to remove the electron receiving surface away from the grid to reduce heat absorbed by the grid. But with the usual three-electrode arrangement w-iththe collector anode at a high positive voltage in order to draw the necessary plate current, this is not entirely feasible.

It is, therefore, an object of my invention to provide an electron discharge device having a high power output and which is suitable for kuse at ultra high frequencies as an amplifier or oS-.v cillator.

More specifically, it is another object of my invention to provide an electron discharge device in which grid emission is substantially reduced.

A still further object of my invention is to provide an electron discharge device in which the electrons may be collected at a low velocity to reduce the energy dissipated in heat. I

These and other objects will appear herein-v after. r

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, butthe 4invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a longitudinal section of an electron discharge device and associated circuit made ac, cording to my invention and Figures 2, 3, 4 and 5 show longitudinal sections of modifications of the electron discharge device shown in Figure l.

In Figure 1 I provide an apparatus which can be used as a high power triode amplier or as an oscillator. It includes an indirectly heated cathode Ill followed by a grid Ii and an anode or collector I2 having cooling iins I2. The en'- velope is formed by means of the conducting col.'- lar member I3 closed at one end by the cupshaped insulating member Ie and at its other end by the insulating collar member I5 and col-"- lector I2 provided with the collar member 21 sealed to the collar I5. The cathode heater III' is provided with a lead I6 extending through the envelope. The cathode I0 is supported by means of the conductors and leads I8 arranged in a circle around conductor` I6 and secured `at one end to the elongated tubular member I'I, 'the other end of the tubular member II being secured to the leads I9 extending through the envelope. Members Il', I B and I9 serve as the other lead for the cathode heater and as the cathode lead. Insulating disc 26 properly centers conductor i5 with respectitoitubular,member Il. The grid II is supported bymeans of Yconducting collar member 2| secured to the tubular conducting member i3 forming part of the tube envelope, the grid and cathode supports being separated `by `means `of the insulating disc 22. The collector I.2.is lpro vided with the member 25 decreasing in diameter toward the grid to protect the sealfand provide-a proper field for the electrons. 'Acrcssfthe opening is placed the wire mesh 26 for bringing about the proper rleld formation through which the electrons pass from the grid :to "the nteriorfof the collector I2. This has the effect of minimizing effective transit time between grid .and an.- ode.

The input circuit connected between the grid and Icathode comprises the elongated outer'tubular member 28 electrically connected to the 'collar'member I3 Yand an inner tubular member 29 capacity coupled at its-inner end to the element '32 'contacted by the spring-like-elements 3e lsecured `to the cathode leads. The 4member S2 electrically connected to the elements 3B provides one conductor through which the heating current fiowsto the cathode heater. 'The'inner conductor IB'is'engaged by meansof a spring clip member positioned on element -33 capacity coupled to element 32. This arrangement provides; means through 'which the cathode direct current flows to the heater and at the same time provides a path Vfor radio frequency currents. It will thus be observed that the grid II, collar 2|, collar I3, member '28, member 29, capacity coupling element 32, leads 30 and I9, tubular member-'Il `and leads 18 provide va coaxial line type resonatorl cavity circuit completely isolated from Vother cirn cuits. .It is tunedby means of the collar-like element 35 slidably supported on vthe inner tubular member29 by means of the 4insulator support '35.

The 4output circuit includes a drum-like member 36 .of larger diameter than tubular member 28 electrically connected to collar 'I3 of the envelope and provide with .a disc-.like element 3T capacity coupled tothe disc-like element 38 posi` tioned transversely .of the 'collar member 21 of the collector I2an'd electrically connected thereto. The diameter tof tubular member28 is of the order Vof one half the diameter of member 36,'as shown in Fig. 1. Energy Vfrom the output tank circuit is coupled Yback to the vinput vcircuit by means Vof the coaxial 'transmission line comprisinginner conductor '39 and 'outer conductor fell. This line is .made vadjustable vto insure proper phase relationship of the 'energy Vfeedback with respectto the voltages inthe input circuit, the 'inner conductor being 'provided with coupling loops -4I and '42. This adjustable 'transmission line is .described in greater detail and claimed'in my copending application Serial N o. 455,175, led 'August 18,1942, now U.'S. Patent"2,440,089, dated April'20, 1948 'and assigned'to the same assignee aszthepresentapplication. These coupling loops `.could be madeadjustable to `control the amount .of feedback. This arrangementpermits both the input and 'output circuits to ibe adjusted independently of eachother and for optimum operating conditions. The output'is taken by means of loop '46 which feeds into uthe coaxial transmission line 41.

"The transformer 43'supplies'heating current for the cathode heater, and resistor rMI provides 'the .and .29.

biasing voltage between the grid and cathode. The anode or collector Voltage is supplied by means of voltage source 45.

In operation an alternating high frequency voltage applied between the grid. II and cathode I0 modulates the electron stream passing to the collector I2. The modulated electron stream in passing across the gap between the grid II and .the surface of the mesh closiu'e member 26 induces -a voltage in the resonant cavity 36 coupled between the grid and the collector, thus energizing .this resonant cavity circuit. Energy is then fed 'back by means of coupling loop 4I, transmission line 39-49 and coupling loop 42 within the coaxial transmission line acting as the input resonant `cavity circuit and comprising members 28 Tuning of the input circuit is accomplished by means of the tuning collar 35 which may be'moved longitudinally of the input circuit.

Output may be taken'from the resonator 36 by means of the coupling loop 46 and coaxial transmission'line 3H. In order to feed the energy from the output resonator to the input resonant lcavity circuit in proper phase, the length of the transmission line 35-42 may be varied by varying the position of the movable U-shaped element 4U' of this line to increase or decrease the length of the line.

In the vapparatus shown in Figure 1, the input and output circuits are completely isolated from each other. Due to the fact that electrons are collected at a surface far removed from the grid II, little radiated heat is absorbed 'by the grid. This eliminates much of the difficulty due to grid emission caused by absorption of heat duc to the energy dissipated "at the surface of the collector. The large collar-like support 2I for the grid acts as a means for 'conducting heat away from the grid rapidly to thus further maintain the grid Vat a lowtemperature. In effect close spacing of 'the electrodes is obtained by means of the structure shown without actually placing the collecting surface close to the grid, thus making the device suitable for use at ultra high frequenvzies where transit time between. the electrodes becomes important. The capacity coupling between the output circuit and the anode or collector permits different voltages to be applied to the circuit and the collector and yet at the same time provides a resonant cavity type of circuit which is particularly suitable for use at ultra high frequencies. The apparatus shown in Figure l can vbe used either as an amplier or oscillatorby controlling the amount and phase of the energy fed into the input circuit.

In Figure 2 is shown a modification of the device shown in Figure 1 and employing ring type seals. The modification shown in this figure has an added advantage .in that the collector may be maintained at a low voltage with respect to some other electrodes within the tube so that the .electrons can be collected at a lower velocity than is Ipossible in the apparatus shown in Figure l, thus further increasing the efficiency of the tube.

The envelope 50 contains an indirectly heated cathode 5I, grid 52, output and accelerator electrode 53, ring-like secondary electron suppressor V5f! and cup-shaped collector 55. The cathode. 'grid vand accelerator electrodes are supported by means of ring members 56, 5l and 58 sealed through the glass envelope. These ring members -provide low loss, low inductance leads for the 'electrodes land merge 'into the circuits utilized with the device.

The input circuit comprises ya `flat drum-like member 68 electrically connected to the ring 51 andl capacitively coupled to the cathode ring 56l by means of the disc-like member 56 electrically connected to the cathode ring 56. The output resonant cavity comprises the drum-like member 6| having a wall 62 capacitively coupled to the flat disc-like element 63 electrically connected to the accelerator electrode ring 58. The two circuits are coupled by means of a transmission line formed by an annular-shaped member 64 surrounding the input circuit. Within member 64 is supported the inner conductor 65 having coupling loop 66 positioned within the input circuit and a coupling loop 81 positioned in the output circuit. This transmission line permits in effect a long line occupying a small space.

Cathode heating energy is supplied by means of the transformer 88 and the grid biasing voltage supplied by means of the dropping resistor 69. The collector electrode and suppressor electrode voltages are supplied by means of the voltage source 10, the suppressor being at the lower potential. The output is taken in the usual way by loop 6|.

With the arrangement shown the accelerator electrode 53 is maintained at a high potential sufficient to draw a large cathode current. Practically no current is drawn by the accelerator 53 so that little energy is dissipated in this electrode. frequency circuit may be maintained at a lower potential than would be the case if it acted as an output electrode and hence electrons are collected at a lower velocity so that energy wasted as heat is reduced. The input and output circuits are completely isolated from each other and the amount of feedback can be controlled as well as its phase by means of the transmission line which can be made adjustable.

In the apparatus shown in Figure 2 an alternating high frequency voltage applied between cathode 5| and grid 52 modulates the electron stream from cathode 5| and which passes to the accelerator and output electrode 53 and is collected by collector 55, secondaries from 55 being suppressed by electrode 54. The modulated electron stream in passing across the gap between grid 52 and accelerator 53 induces a voltage across the gap, causing energization of the resonator 8|. The accelerator 53 is capacitively coupled by means oi the element 58 and wall 62 of resonator 6|, the radio frequency field being confined within this resonator. The collector, therefore, is external to the radio frequency circuit. The input resonant cavity circuit comprises resonator 68 electrically connected to the grid 52 through collar 51 and capacitively coupled for radio frequency to the cathode by means of elements 56' and the radially directed ring-like conducting support 56 of the cathode 5|. Energy is fed back into the input circuit by means of the transmission line comprising the loop 61, coil 65 within the annular box-shaped arrangement 64 and loop 66 within the input resonator. This causes the device to operate as an oscillator.

In Figure 3 is shown a further modification of the construction shown in Figure 2 and provided further with an adjustable transmission line for controlling the phase of feedback. In this modin cation the envelope 15 contains the indirectly heated cathode 16, grid 11, output and accelerator electrode 18, suppressor electrode 19 and collector 88, the cathode heater being supplied through the conductor 8| and conductors 82 mounted in a circle and surrounding the con- Collector 55 which is outside the radio 1 ductor 8| and serving as a support for the cathode. The grid is supported on collar 83, which in turn is supported on leads and support wires 84 mounted in a circle and surrounding conductors 82 and extending through the envelope of the tube. The accelerating electrode is supported by means of radially directed collar 85 connected to and supported by the radially directed ring-like conductor 86 extending through the envelope.

The input circuit comprises the elongated outer tubular member 81 electrically connected to the elongated inner tubular member 88 by means of the closure member 9|. The inner tubular member 88 is capacitively coupled to the collar 89 secured to the outer ends of the leads and supports 82, the insulating collar 96 serving to separate members 88 and 89. The input circuit may be tuned by a member 92 slidable longitudinally of the input circuit.

The output tank circuit includes the resonant cavity structure comprising the member 93 and having one wall 94 provided with an outside annular member 95 in which the conducting disc 96 is supported by means of insulating discs 91 and 98. This disc is provided with spring contact engaging members 99 contacting member 86. This vconstruction permits the envelope to be with` drawn from the output tank circuit and disengaged therefrom. Another wall |88 of the resonant cavity is supplied with spring contact members ||l| engaging the conductors supporting the grid. The cathode heating circuit includes transformer |06 connected to leads 8| and 82 by spring contact members 8| and 82. Voltage source |88 supplies accelerator electrode 18 maintained at a higher potential than the collector by means of voltage source |09. Thus, the envelope and its electrodes may be disengaged from the circuits by pulling the envelope to the right.

Energy may be returned to the input circuit to neutralize input losses or cause the tube to func-v tion as an oscillator by means of the transmission line having inner conductor |05 and outer conductor |82, one end being provided with coupling loop |83 and the other with coupling loop |04. Intermediate the concentric transmission line is a U-shaped adjustable portion comprising the conductors |85 and |82', which are telescopically engaged with the coaxial line. Thus, by varying the length of this line the phase relationship of the energy fed back from the output circuit to the input circuit can be controlled to insure the desired phase relationship. The output is taken by means of coupling loop ||0. Otherwise the apparatus functions in a manner similar to that shown in Figure 2.

In Figures 4 and 5 are shown modifications of the constructions shown in Figure 3 in which the outside condenser coupling arrangement for the accelerator is avoided. In the arrangement shown in Figure 4 the envelope |||l encloses the cathode H control grid li 2, accelerator and output electrode I3, and collector i5 having a mesh conductor |56 positioned across the opening for providing the proper field between the electrodes;

The cathode is provided with an inner heater conductor |i|1 and outer conductors and leads ||8 surrounding conductor ||1, the input circuit being provided by means of the elongated tubular member |29 capacitively coupled to the elongated outer tubular member l2! by means of the collar |23 having a supporting disc |23 connected between it and' 'the inner tubular member |28. Member |2| is connected to grid leadsllZ connected to collar HZ' of grid ||2.

The Voutput felectrode :H3 ls provided with a radially yextending supporting and conducting member H4 electricallylconnectedto the-disc |26 closingone end'of thetubularmember v|24 which is 'closed vat ythe-other-end -by means of the disc |25 lto vprovide the output tank circuit -Of the resonator type connected between the grid and output electrode. The output circuit is energized in the usual way by -inductive eiect when the modulated stream of-e1ectrons passesacross the gap between grid V|f|2 and output electrode |.|3. Tuning 4of the `input `circuit is accomplished by means-o the-collar member |28 movablelongitudinally'of the input circuit,and .theoutput circuit istuned by-meansiof the collar |20 supported on insulating elements |30 also slidable axially of the output icircuit.

:Coupling between the input and-output circuits is provided by means of the coupling loop |3|, the outputibeing taken -by means of outputcoupling loop 132. Cathode heating current is yprovided by voltage source '|33-and proper'bias on the grid bymeans of droppingresistor |34. The collector voltage is supplied by means of .voltage source |35.

Thus the electrode |-|3, which is maintained atcontrol grid'potential serves to minimize capacitance between the control v.grid and collector. Largecapacitancebetween the collector and electrode H3 serves to-by-pass radio frequency currents. The electroncollectingarea of thecollector is far removedifrom the control grid and cathode lso that the gridlmay `be run-quite cool.

In Figure vis shown another arrangement .in which the collectorfmaybe maintained at a lower positive potential lthan the output electrode or accelerator. :A 'separate high positively biased electrodeisused to getrhighpeakcurrents. This electrode does not take current. The `collector is outside ofthe radio frequency circuit and has a potential applied only suficient to -collect the electrons. Thus, there results a-high eiciency apparatus of the kind shown in Figure 3, but without the need of an external fcapacity coupling arrangement.

Tn this arrangement the envelope |40 contains the-cathode 50, and grid |60 supported on collar |61. The screening and shielding electrode |62 is supported by the radially extending support and rlead arrangement |63 which extends through the lwall of the envelope. The collector |64 is positioned to receive electrons from the cathode, the accelerator electrode |65 being positioned within the screen electrode |62.

The input circuit comprises'the elongated outer tubular conductor connected'to the grid leads and supports IGI' and the elongated inner tubulanmember'ii which is connected to the cathode leads and support |69. The output'circuit comprises the .resonant cavity circuit |61 having a wall |69 electrically connected to the radial leads |63 and another wall |66 electrically connected to the tubular member |10. The two circuits are coupled by means of the coupling loop |12. Cathode heating current is supplied by means of transformer |14 through lead |68 and leads |69 and grid bias voltage bymeans of voltage source |13. The accelerator land collector voltages are suppliedby potential `sources |16 and |11. The output is taken by coupling loop |30.

In 'the last arrangement described the collector is maintained at a lower potential than the accelerator.

-High frequency apparatus made according to my invention eliminates orsubstantially reduces the difiiculties due to Vgrid emission. -Eiliciency is increased by providing means for collecting the `electrons at low velocity. This is `accomplished while `at the same time providing high power outputs whether the apparatus is used as an amplier or oscillator. My apparatus also provides ya ready means for disconnecting the electrodes from the associated circuits, thus making available an `electron discharge device and an'associated circuit apparatus permitting ready replacement incase of damage to the tube or where replacement is desired for other reasons.

While I have indicated the preferred embodiments of my invention of which I am now aware andvhave also indicated only one specic application for which my invention may be employed. it will be apparent that my invention Ais by no means limited to the exact forms illustrated-or the use indicated, but that many variations may be made in the particular structure used and the purpose -for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is:

l. A high frequency apparatus including a rst-drum-shaped cavity resonator comprising a pair ci' closely spaced planar conductors -positioned in iace-to-face relation and forming boundaries-or" said first cavity resonator between them, means comprising a pair of elongated coaxial conductors extending at right angles to said planar conductors and forming boundaries of a second cavityresonator'contiguous with the rst cavity resonator, the maximum transverse dimension of said coaxial conductors being substantially smaller than that of said planar conductors and an electron discharge device `extending within said first cavity resonator and having a cathode, grid-and another electrode, said first resonator being coupled between said grid and other electrode, and said second resonator coupled between said cathode and grid.

y2. A high frequency apparatus includinga pair of oppositely disposed apertured disc-like conductors 'connected at their outer edges to form boundaries of a vdrum-shaped iirst cavity resonator, an electron discharge device extending vwithin said first cavity resonator and having a cathode, grid and-another electrode, -said grid andother electrode being connected to said disclike conductors, and a coaxial-line second cavity resonator comprising a pair of axially elongated concentric conductors coaxial with said disc-like conductors, said concentric conductors being connected together at one Lend and connected to said grid `and said cathode at the other end.

3. A high frequency apparatus including an envelope containing a cathode, grid and another electrode in the order named, a rst drumshaped cavity lresonator surrounding said envelope and coupled between said grid and other electrode and comprising a pair of oppositely disposed plate-like members closed at their peripheries by a conducting collar and providing an output resonator, and a second resonator coupled between said cathode and grid and comprising an elongated coaxial line including an outer tubular member coupled to one of said plate-like -members and an inner tubular member coaxial with said'outer tubular member Vand coupled to said cathode land providing an input resonator, said outer and inner tubular members having a maximum transverse dimension of the order of one-half that of said plate-like members.

4. A high tfrequency apparatus including an envelope containing a cathode, grid and another electrode in the order named, a rst cavity resonator surrounding said envelope and coupled between said grid and other electrode and comprising a pair of oppositely disposed plate-like members closed at their peripheries by a conducting collar and providing an output resonator, and a second resonator coupled between said cathode and grid and comprising an elongated coaxial line including an outer tubular member coupled to one of said plate-like members and an inner tubular member coaxial with said outer tubular member and coupled to said cathode, and providing an input resonator and conducting means coupling said resonators together for providing feedback from the output resonator to the input resonator, said outer and inner tubular members having a maximum transverse dimension substantially smaller than that of said platelike members.

ANDREW V. HAEFF.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

